The present invention relates to an optical head device for recording and reproducing apparatus which writes information optically into an optical information recording medium such as a photo-magnetic disk and reads information from the medium.
A conventional optical head (optical pickup) which is capable of recording, reproducing and erasing information is composed of many components which takes much time to be positioned and aligned, and lacks in functional stability, which will be described in more detail later. Especially, a halfwave plate and a Wollaston prism, used to detect the direction of polarization of light require precise positioning.
It is therefore an object of the present invention to provide an optical head device for recording and reproducing information which is composed of a reduced number of components, eliminates the need of a halfwave plate and a Wollaston prism, and is compact and easy to assemble.
The above object of the present invention is achieved by an optical head device that can record and reproduce information, which includes a light source and a polarization beam splitter which transmits 100% of the p-polarized component of a light emitted from the light source and reflects the s-polarized component of the emitted light in a direction perpendicular to the optical path of the emitted light. The head device further includes an optical piece which directs the reflected s-polarized component upon a photomagnetic disk and directs the light reflected from the photomagnetic disk toward the polarization beam splitter. The light reflected from the disk contains both a p- and an s-polarized component. The head device also includes a beam splitter which receives the directed light reflected from the photomagnetic disk and splits it into two beams which propagate in directions different from one another. The beam splitter varies the intensities of the two split beams, the relative intensities being determined by the magnitude of the p-polarized component of the light received by the splitter. These two beams are then converged onto photo-detecting elements which are used to reproduce the binary data corresponding to information stored in the photomagnetic disk.
The above object of the present invention is also achieved by an optical head device that can record and reproduce information, which includes a light source, a polarization beam splitter that transmits 100% of the p-polarized component of a light emitted from the light source and reflects the s-polarized component of the emitted light in a direction perpendicular to the optical path of emitted light. An optical piece then reflects the reflected s-polarized component onto a photomagnetic disk and directs the light reflected from the disk toward the polarization beam splitter. The light reflected from the disk contains both a p- and s-polarized component. The light reflected from the disk is then split into two beams, the first beam propagating along the optical path of the directed light and the second beam propagating in a direction perpendicular to the first beam.
The beam splitter includes second portion for splitting the first beam into a third and fourth beam which propagate into different directions, the relative intensities of the third and fourth beams are determined by the magnitude of the p-polarized component of the first beam. The beam splitter is further adapted to converge the third and fourth beams onto photo-detecting elements which then are used to reproduce data corresponding to information stored in the photomagnetic disk.
The above and other features and advantages will be clarified from the following description of a preferred embodiment thereof when taken with reference to the drawings.